Download Coke Making - Materials and Heat Balance in Metallurgical Processes - Lecture Notes and more Study notes Materials Physics in PDF only on Docsity! Lecture 27: Material balance in Coke making Illustration‐I Do yourself Illustration‐I In coke‐making, it is often required to calculate the amount of coke, coke oven gas and tar produced per ton of coal. This can be done by performing elemental balance. For this purpose ash, C, N, H and O balance can be done to obtain the require information. This is illustrated by the following problem 1. By product coke ovens are surrounded by air. There may occur leakage of air in the oven. Consider a coke‐ oven surrounded by moist air, (The air is at 750 mm Hg pressure and 26 temperature) . The relative humidity of air is 40%. It carbonizes coal of the composition (Wt%) C76.1, H 4.6, N2.3, S 1.9,O 2.5, H O 6.3 and ash 6.3. The following product and by products are produced: Product: Coke (Wt %) C 85.2, H 1.9, O 2.2, N 0.8, S 1.2 and Ash 8.7 By –product: (a) Coke oven gas (vol % dry basis) and C6H6 1.1,C2H4 2.7,CH4 4.4, CO 1.7, CO2 1.3, H2 36.5, N2 6.9, O2 2, H2S2.1 and NH31.3 (b) Tar (40 kg/ton of coal) analysis (Wt %) C=89.4, H 4.5, N 1.1. and incombustibles Rest. Required per ton of Coal i. Amount of coke /ton of coal g. al. ii. Amount of coke‐oven gas iii. fraction of S in coke and coke oven gas iv. Amount of air leakage: The vapor pressure of moisture in air at saturation is 25.21 mmH v. Calorific value in coke and coke oven gas in terms of fraction of calorific value of Co Solution: Basis of calculation: 1000 kg coal i. Amount of coke /ton of coal Ash balance is used to determine the amount of coke. Let x kg is amount of coke. . . x 724.1 kg coke Answer. ii. Amount of coke oven gas can be calculated by performing C balance et y kg is the amount of Cokes oven gas C from coal= C in tar+ C in coke + C in Cokes oven gas L . . . y 6 0.01 2 0.027 0.344 0.117 0.013 y solving we get y= 15.357 kg mole i. Sulphur distribution a) f fraction of S in coke S S B ii 0.457 Ans. ) fraction of S in coke oven gas . . . b 0.543 Ans. . To calculate amount of air leaked in to coke oven. N balance is to be done. N is inert. mposition of moist air. It follows drom Dalton’s law; Where p is partial pressure. O H O iV Let Z kg mole is amount of air leaked. In this problem air is moist. We have to find co pN pO pH O 750 mm RH Relative humanitiy H V H O V H O PN2 + pO2 + RH x p S H2O = 750 pSH2O, we get after simplification moles of N from moist air Substituting the value of RH and pN 584.533, pO2 155.382 and p H2O 10.084 . 0.7794 N2 from coal+ N2 from air = N in coke + N in tar+ N2 coke oven gas . in 0.7794 Z . . . 0.069 0.0065 15.357.
